This invention relates generally to a dispenser, especially for a high viscosity product, and more particularly to such a dispenser capable of dispensing the product in metered amounts and without clogging as a jet of air is discharged through a hollow valve spindle for removing any product remaining at the discharge orifice.
Difficulties have been encountered during the dispensing of products, especially high viscosity adhesives, because of the "stringing" of the adhesives which develop when being applied to a workpiece. Dispensers which have been used for these purposes typically include a plunger which, when actuated, compresses the adhesive and forces it through a discharge nozzle. However, because of the high viscosity of the material being dispensed, it is difficult to precisely control the metered amount of dispensed product. After a desired quantity of adhesive is applied to the workpiece, the dispensed adhesive continues to cling to the discharge nozzle because of the "stringing" effect which typically occurs. Therefore, the operator must reverse the plunger stroke for suctioning the strings back into the nozzle in an attempt to sever them from the dispenser. Unintended areas of the workpiece may thus be coated by the indiscriminantly falling strings or by residual portions of the adhesive remaining at the nozzle tip. Moreover, the discharge nozzle may become clogged with residual adhesive remaining after repeated use. And, dermatological problems may arise in the event of prolonged skin contact of the adhesive by the operator.